Recently, new analysis methods and methodologies known as DNA microarray methods (DNA chip methods) which allow one-operation expression analysis of numerous genes, have been developed and now attract attention. These methods do not differ in principle from conventional methods in respect of the fact that they are nucleic acid detection and quantification methods based on nucleic acid-nucleic acid hybridization. However, a major characteristic of these methods is the utilization of a microarray or chip which comprises a large number of DNA fragments aligned and immobilized at high density on a flat substrate. Examples of a specific method of using a microarray method include hybridizing a sample of expression genes of a test subject cell labeled with fluorescent pigment on a flat substrate slice, allowing mutually complimentary nucleic acids (DNA or RNA) to bind with one another and after labeling these locations with fluorescent pigment, rapidly reading with a high resolution analysis device. In this way, respective gene amounts in a sample can be rapidly estimated. That is, the introduction of these new methods has enabled a reduction in reaction sample amount, and high volume, rapid, systematic analysis and quantification of these reaction samples with good reproducibility.
As methods of producing these DNA microarrays, there have been disclosed a method wherein DNA is compartmentalized and immobilized on a glass substrate, and a method wherein nucleic acids are synthesized one by one on compartmentalized regions on a silicon substrate using photolithography techniques used in the production of semiconductor chips (U.S. Pat. No. 5,445,934; U.S. Pat. No. 5,774,305).
Further, there have been disclosed a method of a obtaining a DNA microarray wherein DNA is immobilized on linear bodies comprising glass or high molecules, and these linear bodies are sheet-rolled together with adhesive, and sliced in the direction of the cross-section of the fiber (Japanese Patent Publication (Unexamined Application) No. 11-108928); a method of obtaining a DNA microarray wherein a plurality of fibers have DNA etc. immobilized thereon, these are bundled together and this bundle is sliced across the longitudinal direction of the fibers DNA microarray (Japanese Patent Publication (Unexamined Application) No. 2000-245461); and further a method of obtaining a DNA microarray wherein a plurality of through-holes are made in a resin block, and after the these holes are made to carry DNA etc., the block is sliced (Japanese Patent Publication (Unexamined Application) No. 2000-78998). Because these methods of production allow a plurality of microarrays to be prepared by repeated slicing, they are particularly preferable methods for mass producing chips having the same sequences.
For example, in general, detection of specific DNA within an analyte using the DNA microarrays exemplified above, is performed by fluorescence-labeling probe DNA immobilized on the chip, or analyte DNA, irradiating the probe or analyte which has formed a hybrid due to performing operations such as hybridization etc., with fluorescence excitation light from an external source, and detecting fluorescence excitation emitted from the fluorescent molecules.
However, when detecting an organism-related substance such as DNA which is contained in an analyte in only trace amounts, fluorescence other than that emitted from the probe or analyte, specifically, self-fluorescence of the substrate etc., carrying the probe, is detected as noise, and there was the problem that trace amounts of an organism-related substance could not be detected.
Further, a method of producing a plurality of microarrays by repeated slicing is superior in respect of the fact that a large amount of microarrays having the same arrangement can be mass produced. However, there is the problem that curvature of the microarray occurs.